Off road work vehicles in the agricultural, mining and construction fields, such as tractors, and the like, have traditionally operated with manual steering. Improvements in control system design and related position sensing technology, such as global positioning systems (GPS), including differential correction systems, as well as real time kinematic (RTK) satellite navigation have led to an increase in the use of automatic guidance control systems for these vehicles. The combination of improved navigation input signals precisely identifying vehicle position and speed with sophisticated on board vehicle electronic control systems allows for automatic guidance systems capable of steering the vehicle with a high degree of accuracy when traversing terrain.
To provide this control, the prior art teaches using satellite positioning information by an onboard vehicle navigation control system to accurately determine and control a vehicle's position while operating in a field. A preplanned route, based on information previously known about the terrain of the field, or a control system generated route may be used. The control methods are well known in the art, and may involve multiple position transmitters or receivers, with various signals used to derive vehicle location, elevation, direction of travel or heading, and speed.
The task of precision guidance of an agricultural vehicle involves not only accurately determining vehicle position in a field, but also defining an efficient array of paths or swaths to be followed by the vehicle that will create an overall swath pattern that efficiently and effectively covers the crop area of a field. The pattern must be located and oriented on the field, and the physical characteristics and limitations of the vehicle and coupled implement must be identified and provided to the navigation system. Implement or header width, location of the implement or header relative to the vehicle, and limitations of the vehicle and associated implement movement, such as minimum turning radius, must also be considered. With this information it is possible to define a series of swaths for the vehicle to travel in an attempt to cover all cultivatable portions of a field without unnecessary gaps or overlaps.
For a rectangular region of a field, swath patterns are typically generated including side by side swaths spaced evenly at the width of the implement or header to cover the field without substantial gaps or overlaps. However, unless the width of the field is an exact multiple of the implement or header width, generation of swath lines in this manner will result in at least one, usually the last swath of the field having a different width, generally more narrow than the width of the implement or header. This swath represents an opportunity for gaps or overlap in the region of the field.
Often swath patterns must be generated for fields, or regions thereof, that are not rectangular but have opposite, diverging sides. One such region can be described as having a first end boundary, a second end boundary opposite to the first end boundary, a first side boundary and a second side boundary opposite to the first side boundary, and the first and second side boundaries extending divergently between the first and second end boundaries. This region is typically characterized as having one end boundary wider than the other end boundary. The methods of generating swath patterns for rectangular fields, when applied to this type of field, typically results in point rows, or shorter swaths adjacent to the wider end of the field. Rather than extending between the end boundaries, the shorter swaths of point rows extend between an end boundary and a side boundary. Since work vehicles generally use wide implements or headers, the additional turns required for planting along the shorter swaths is difficult and time consuming.
Generating swath patterns including point rows presents other inherent disadvantages also. Point rows, as well as the smaller last swath of the rectangular field, tend to cause inefficient use of seeds, applied nutrients, chemicals, and the like, especially when the operator is unable to control the operation of individual rows or sections of an implement. In this case, working the point rows by overlapping previously worked swaths can result in damage to crops and/or reduced crop yield. Working the point rows by driving outside the field boundary, if possible, results in wasted product outside the field boundary. When the operator can control the operation of individual rows or sections of the implement, the effective width of the implement can be reduced, and overlap of the output disabled rows over previously worked rows does not result in wasted resources by working the same rows twice. However, the process of working point rows is still difficult and time consuming because the operator must determine which rows and/or sections to disable and then drive the work vehicle over the shorter point rows. Finally, failure to work the point rows and/or the shorter or more narrow swaths results in an unplanted section of the field, which allows weeds to grow and seed weeds into other parts of the field.
Another disadvantage presented by generation of swath patterns in the above described manner is the lack of control over the position of the work vehicle upon completion of work in the field. An operator may prefer to start and complete work on the field at the same end to avoid having to drive the length of the field in a non-operational mode once work on the field is complete. Alternatively the operator may prefer to complete work on the opposite end of the field so as to be closer to another region to be worked. Non-operational passes of a work vehicle over a field result in wasted time, resources, unnecessary soil compaction, and the like.
What is sought is a method to generate swath patterns for a quadrilateral shaped field having opposite sides which divergently extend between opposite ends which overcomes at least one of the problems, shortcomings or disadvantages set forth above.